SITE INFORMATION AND CORRESPONDENCE_FILE 2

Home Browse Search

Site Background Information: Chapin Brothers Investments, Inc. Page 13 of 19 Based on the ground water aquifer pumping test results, AGE recommended remediation by extracting petroleum-impacted ground water from a network of wells,at approximately 5 GPM total flow. Based on the site's estimated radius of influence of at least 35 feet and site specific aquifer characteristics inferred from the pumping test,AGE believed that ground water extraction from four on site wells and three proposed installed ground water extraction wells will effectively stabilize the ground water plume and inhibit further migration of petroleum-impacted ground water off-site; further reducing the overall mass of dissolved hydrocarbons at the site.Extracted ground water was to be treated through an on-site ground water pump-and-treat system. The ground water pump and treat system would utilize granular activated carbon (GAC) to address TPH-g, and BTEX in extracted ground water. Following treatment, water could then be discharged into the City of Stockton under a Municipal Utility District permit. INSTALLATION OF GROUND WATER RECOVERY WELLS Between December 2001 and March 2002, three ground water recovery wells, a ground water treatment system and associated piping were installed at the site.Ground water remediation system installation and operation were performed in accordance with procedures described in the approved Remedial Action Work Plan Addendum, dated 28 June 2001. Between 21 and 22 December 2001,three soil borings were advanced using a truck-mounted CME 75-HT drill rig equipped with continuous flight 12-inch augers. The soil borings were advanced to a depth of 30 feet bsg. Soil borings EW 1,EW-2 and EW-3 were single-completed as ground water extraction wells utilizing a schedule 40,6-inch diameter blank polyvinylchloride(PVC)well casing and a perforated, 6-inch diameter PVC well casing (0.020-inch slot). The wells was installed by placing the PVC well casing assembly through the hollow stem of the augers to the total depth of the boring.The augers were incrementally raised as filter pack material consisting of a 50/50 blend of fine grained aquarium gravel and#3 Monterey Sand was slowly poured down the annulus between the well casing and the inner wall of the hollow stem auger. The filter pack was placed adjacent to the screened casing from the bottom of the boring to a point approximately two feet above the top of the screen. Following filter pack placement,a surge block was inserted into the well casing and was alternately raised and lowered (surged) repeatedly for approximately 20 minutes to settle the filter pack material. A nominal three-foot seal of bentonite pellets was placed above the filter pack and allowed to hydrate with clean tap water. The remaining annular space was backfilled with portland cement. Advanced GcoEnvironmental,Inc.